Microprocessor device with integrated auto-loaded timer

Abstract

A microprocessor device with an on-chip integrated auto-loaded timer is used in an adapter for a communications loop of the token-passing local area network type. The network has a number of stations coupled to a closed one-way signal path, and each station has a host processor with a host CPU and memory. The microprocessor device with integrated auto-loaded timer is part of an adapter coupled to the host processor. A message frame to be transmitted is copied into a local read/write memory in the adapter by way of the host system bus and a local bus, under initiation by the host CPU. A transmit-and-receive controller is coupled to the local bus to directly access the local read/write memory; when this station has access to the loop (i.e., receives a free token) the transmit-and-receive controller copies the message frame from the local read/write memory to the outgoing signal path, converting from parallel to serial. When the transmit-and-receive controller receives a message addressed to this station, it converts it from serial to parallel, and copies the message frame into the local read/write memory via the local bus, interrupting the local CPU. The message frame is then copied from the local read/write memory to the main memory.